The closest known planet outside our solar system is Proxima Centauri b. It orbits the red dwarf star Proxima Centauri, which is part of the Alpha Centauri system, our closest stellar neighbor.

Here's the breakdown:

* Distance: Proxima Centauri b is about 4.24 light-years away from Earth.

* Star: Proxima Centauri, a red dwarf star.

* Size: Approximately 1.17 times the mass of Earth.

* Orbit: It orbits its star every 11.2 days.

However, it's important to note:

* Habitability: While it's considered a potentially habitable planet, its proximity to the star means it likely experiences intense radiation and tidal locking.

* Discovery: It was discovered in 2016 using the radial velocity method, which detects the "wobble" of a star caused by a planet's gravitational pull.

While Proxima Centauri b is the closest known exoplanet, new discoveries are constantly being made, so the closest planet could change in the future.